This application relates to a panic stoplight system for automobiles or similar vehicles, and to a fluid pressure switching device for use in such systems.
Conventional automobiles and similar vehicles include rear lights which are turned on when the vehicle brakes are applied to warn the operator of a following vehicle that the forward vehicle is decelerating. During daylight operation, the rear lights are simply turned on when the brakes are applied. During nighttime operation, the rear lights usually increase in intensity when the brakes are applied. A warning system of this type gives no indication as to how rapidly a vehicle is decelerating. The brake lights are on with the same intensity anytime the brakes are applied, regardless of the magnitude of the braking force.
Many systems have been proposed for providing different signals related to the deceleration rate of the vehicle. One proposed system includes inertia switching devices responsive to changes in vehicle momentum for turning the warning lights on. These systems do not warn a following operator of certain emergency conditions such as icy pavement. An operator of a vehicle may see an emergency condition ahead and forcefully apply the brakes. If the pavement is icy, the vehicle will simply continue with little change in momentum. With an inertia-type of switching device, the operator of a following vehicle will be unaware of the attempted panic braking of the forward vehicle.
Other proposed systems include a plurality of different lights of different colors. Each light is related to a certain operating mode of the vehicle. For example, a green light may indicate that a vehicle is traveling along normally; a yellow light that the vehicle is decelerating slowly; and a red light that the vehicle is decelerating rapidly. Systems of this type are very expensive because they require a plurality of switching devices and lights. In addition, an operator of a following vehicle may have his eyes off the forward vehicle momentarily and not see a light change from yellow to red. Upon seeing the red light, it will take the operator of a following vehicle at least a split second longer to react and this could be too late to prevent an accident.
Other systems of the type described include complicated switching arrangements for flashing the rear lights at various rates and intensities proportional to the deceleration rate. A system of this type is highly effective only if the operator of a following vehicle always has his eyes on the forward vehicle so that changes in the flashing rate will be readily apparent. An operator who momentarily looks in his rearview mirror or on some other scene and then notices the forward vehicle lights blinking will not be readily aware of whether the blinking rate is representative of normal or panic deceleration.
In all prior systems of the type described, the warning signal goes off as soon as panic braking ceases. This has the disadvantage that if a vehicle operator applies the brakes in a manner representative of panic braking for only a second or two, and the following operator momentarily has his eyes off the forward vehicle, he will not be aware that the forward vehicle has rapidly decelerated. Systems having a plurality of different lights or lights which blink at different rates depending upon the deceleration rate can also create confusion and pose a serious distraction under crowded multi-lane traffic because an operator would see many different lights blinking at many different rates.